Add CreateAction endpoint to ActionController

Introduced a new asynchronous `CreateAction` method in the
`ActionController` class to handle HTTP POST requests for
creating "rec actions". The method accepts a `CreateRecActionCommand`
object from the request body, processes it using `mediator.Send`,
and returns a `201 Created` response using `CreatedAtAction`.

src/ReC.API/Controllers/ActionController.cs

@@ -14,4 +14,10 @@ public class ActionController(IMediator mediator) : ControllerBase
         await mediator.InvokeBatchRecAction(profileId);
         return Accepted();
     }
+
+    public async Task<IActionResult> CreateAction([FromBody] CreateRecActionCommand command)
+    {
+        await mediator.Send(command);
+        return CreatedAtAction(nameof(CreateAction), null);
+    }
 }